1. Field of the Invention
The present invention relates to an image transfer sheet which transfers an image formed thereon onto a receiving material and an image transfer method using the image transfer sheet.
2. Discussion of the Background
Recently, a variety of image forming apparatus have been developed and utilized for copiers and printers for computers or the like. These image forming apparatus include, for example, electrophotographic copiers in which a toner image formed on an image bearing member is transferred onto a receiving material, and printers in which an ink image is formed on a receiving material by imagewise heating a thermal transfer recording material or a sublimation thermal transfer recording material or by imagewise shooting an aqueous ink or an ink fused by heat. The images formed with these image forming apparatus are not only used for a purpose of reading or viewing, but also tried to be applied for various new applications.
As one of these new applications of the images, a method is proposed in which the images are transferred onto an image receiving material, such as cloth, leather, canvas, plastics, paper, wood, glass, china, metals or the like. This method is useful for manufacturing a small lot of made-to-order goods having original pictures thereon, such as T-shirts, sweat shirts, aprons, jackets, cups, plates or stained glass, and for manufacturing small lot of pictures duplicated on canvases, which are mainly manufactured for individuals. Currently, since full color copiers are developed and high quality full color images can easily be obtained, the demand for this method is increasing more and more.
An image transfer sheet used for the image forming method in which toner images formed on the image transfer sheet are transferred onto such an above-mentioned image receiving material is discussed, for example, in Japanese Laid-Open Patent Publication No. 52-82509. This Publication discloses an image transfer sheet including an adhesive layer, which is formed on a supporter and which includes an adhesive selected from the group consisting of silicones and fluorine-containing polymers, and an under coat layer, which is formed on the adhesive layer and which is consisting of a polymer meltable at a relatively low temperature. When a toner image, which is formed on the undercoat layer of the image transfer sheet, is brought into contact with a receiving material such as cloth etc. While being heated and pressed, the toner image is transferred onto the receiving material together with the undercoat layer.
In the present application, this method in which an image is transferred on a receiving material upon application of heat and pressure is hereinafter referred to as a dry-type image transfer method.
Another image transfer sheet is disclosed in, for example, Japanese Laid-Open Patent Publication No. 8-108610. This Publication discloses an image transfer sheet in which a release layer including a water-soluble resin as a main component, an adhesive layer which can adhere to a receiving material, an image bearing layer on which an image is to be formed, are overlaid on a substrate permeable to water (hereinafter referred to as a water-permeable substrate) in this order. After an image is formed on the image bearing layer of the image transfer sheet, the transfer sheet is dipped into water to dissolve the release layer, and thereby a combination layer of the image bearing layer/adhesive layer can be released from the substrate. The combination layer of the image bearing layer/adhesive layer, which has been released from the substrate while sliding on the surface of the substrata, is then adhered to a receiving material such as glass, plastics etc., and dried to form a transfer image on the receiving material.
In the present application, this method in which an image formed on a transfer sheet is transferred on a receiving material including a step of dipping the transfer sheet into water is hereinafter referred to as a wet-type image transfer method.
The wet transfer method is superior to the dry transfer method because the wet transfer method does not need an additional apparatus for heating end pressing a transfer street, and an image can tee easily transferred onto a receiving material which deforms or breaks upon application of heat and pressure. In addition, the wet-type image transfer method has en advantage in that an image can be easily transferred onto a receiving material having a curved surface.
However, the transfer sheet for use in wet-type image transfer methods disclosed in Japanese Laid-Open Patent Publication No. 8-108610 has the following drawback. When an image formed on the combination layer of the image bearing layer/adhesive layer, which has been released from the substrate in water, is transferred onto a receiving layer, the image tends to be wrinkled particularly when the image is made of a toner formed by electrophotography and an ink formed by a thermal transfer method.
Because of these reasons, a need exists for an image transfer street which is used for wet-type image transfer methods and which can form a transferred image having good image qualify on a variety of receiving materials without making wrinkles, and an image forming method using the image transfer sheet.